Method and system for acoustic communication

ABSTRACT

An acoustic transducer arrangement and system and method utilizing the same are presented. The acoustic transducer arrangement includes: an acoustic transmitter assembly including an array of transmitter elements operable to generate together a multi-frequency acoustic signal; and a control unit preprogrammed to operate the acoustic transmitter assembly in accordance with digital data stream indicative of a received signal to generate the multi-frequency acoustic signal indicative of the received signal.

FIELD OF THE INVENTION

This invention is generally in the field of communication techniques,and relates to a communication method and system utilizing acousticsignals.

BACKGROUND OF THE INVENTION

Acoustic computer communication techniques have been developed as analternative to IR and RF wireless communication. Unlike IR and RF,acoustics does not suffer from such unexpected environmental conditionsas sunlight, rain, metal objects, and can be “hidden” from people if itsfrequency is higher than 20 kHz. Indeed, IR usually requires directvisibility and is hampered by sunlight or bright interior light. Also,IR has such unexpected features as propagation through materials (thatare not transparent in visible light) and reflection from variousmaterials. RF, in turn, suffers from interference problems and can beblocked by metallic objects.

Various advantageous features of the acoustic-based communication, aswell as examples for protocols for acoustic transmission, are disclosedin the following article: “Things that talk: Using sound fordevice-to-device and device-to-human communication”, V. Gerasimov and W.Bender, IBM Systems Journal, Vol. 39, Nos 384, 2000, pp. 530-546. Thisarticle suggests using ultrasound for device-to-device communication andusing audible signals when devices communicate to human listeners.

Methods for communicating with an electronic device utilizing acoustictransmission below 100 kHz are disclosed in WO 00/21020 and WO 00/21203.WO 00/21020 describes a smart card comprising a memory for storinginformation; at least one transmitting or receiving antenna (which maybe acoustic antenna); and a low frequency circuit, for handlinginformation associated with said antenna and said memory, whichinformation is modulated at a modulation frequency of between 5 kHz and100 kHz. WO 00/21203 describes a method of communicating with anelectronic device via acoustic signals with the frequency below 50 kHz.This technique consists of providing a computer having an audible soundreceiving and generating sub-system including a microphone; transmittingfrom a source at least one ultrasonic acoustic signal, encoded withinformation to the computer; and receiving said at least one signal bysaid microphone, to be detected by said computer.

SUMMARY OF THE INVENTION

There is a need in the art to facilitate communication between variousdevices by means of data transmission in the form of acoustic signals toenable fast transmission with high signal to noise ratio.

The present invention provides a novel method and system for acousticcommunication capable of concurrently generating a modulatedmulti-frequency acoustic signal representative of the entire data sample(multi-bit data stream), and allowing for concurrently receiving anddemodulating the entire data sample. This is implemented by using anarray of acoustic transmitters and operating them to produce together amulti-frequency acoustic signal modulated in accordance with a datasample, and utilizing one or more acoustic receivers (preferably, atleast two such receivers) for collecting a multi-frequency acousticsignal.

The present invention, according to its one broad aspect provides anacoustic transducer arrangement comprising: an acoustic transmitterassembly including an array of transmitter elements operable to generatetogether a multi-frequency acoustic signal; and a control unitpreprogrammed to operate the acoustic transmitter assembly in accordancewith a digital data stream indicative of a received signal to generatethe multi-frequency acoustic signal indicative of the received datastream.

Preferably, the acoustic transducer arrangement also comprises anacoustic receiver assembly operable to receive a multi-frequencyacoustic signal; and at least one input/output port forinputting/outputting a data stream in the form of at least one of thefollowing signal formats: radio-frequency signal, infra-red signal, andelectrical signal. The control unit is thus connected to theinput/output port for receiving the data stream that is to betransmitted through the transmitter assembly as an acoustic signal andfor outputting a data stream representative of the receivedmulti-frequency acoustic signal, and is also preprogrammed to processdata representative of the received acoustic signal to demodulate itinto an output data stream.

Each of the transmitter elements has a resonance frequency differentfrom that of the other elements and is independently operated by thecontrol unit to generate an acoustic wave component. The multi-frequencyacoustic wave, generated by the array of transmitter elements, is thus asuperposition of sinusoidal signals of the multiple different frequencycomponents. The resonance frequency of the transmitter element ispreferably in a high ultrasound range, higher than 20 kHz.

The number of the multiple different frequency components may be equalto the number of the transmitter elements in the array. Alternatively,the acoustic transmitter assembly may comprise at least one electricallyconductive membrane accommodated in a path of the acoustic wavecomponent generated by the transmitter element and operable to oscillatewith a frequency different from that of said acoustic wave component. Inthis case, the number of said multiple different frequency componentsforming the acoustic signal is higher than the number of the transmitterelements in the array, since two different frequency components areproduced by the same transmitter element. One or more such electricallyconductive membranes may be accommodated in the paths of all theacoustic wave components generated by the transmitter elements.

Preferably, the control unit is operable to modulate the data stream tobe indicative of a network address of an associated communicationstation connectable to a communication network.

The acoustic signal may be frequency modulated in accordance with thedata stream. For example, a presence of a specific frequency in themulti-frequency acoustic wave is indicative of binary “1” and absence ofa specific frequency is indicative of binary “0”. Alternatively, oradditionally, the acoustic signal may be amplitude modulated.

According to another broad aspect of the present invention, there isprovided an acoustic transducer arrangement comprising:

-   -   (i) at least one input/output port for inputting/outputting a        data stream in the form of at least one of the following signal        formats: radio-frequency signal, infra-red signal, and        electrical signal;    -   (ii) an acoustic transmitter assembly comprising a piezoelectric        element operable to generate an acoustic wave component with a        first frequency corresponding to its resonance condition, and an        electrically conductive membrane accommodated in a path of said        acoustic wave component and operated to oscillate with a second        frequency different from the first frequency, the acoustic        transmitter assembly being thereby operable to concurrently        produce a two-frequency acoustic signal;    -   (iii) an acoustic receiver assembly for receiving an acoustic        signal;    -   (iv) a control unit connected to the input/output port for        receiving the data stream that is to be transmitted through the        transmitter assembly as an acoustic signal and for outputting a        data stream representative of the received acoustic signal, said        processor assembly being preprogrammed to operate the acoustic        transmitter assembly to generate the two-frequency acoustic        signal modulated in accordance with the received data stream,        and to process data representative of the received acoustic        signal to demodulate it into an output data stream.

According to yet another aspect of the present invention, there isprovided an acoustic transmitter assembly for producing amulti-frequency acoustic signal, comprising at least one piezoelectricelement operable to generate an acoustic wave component of a firstfrequency corresponding to the resonance frequency of the piezoelectricelement, and an electrically conductive membrane accommodated in a pathof said acoustic wave component and operable to oscillate with a secondfrequency different from the resonance frequency of the piezoelectricelement, said multi-frequency acoustic signal being therefore asuperposition of at least said first and second frequency components.

According to yet another aspect of the invention, there is provided amethod for use in data exchange between communication systems, themethod comprising:

-   -   (i) in response to a signal representative of a digital data        stream, processing said data stream to translate it into a        predetermined sequence of frequencies, and concurrently        operating an array of acoustic transmitters to generate a        multi-frequency acoustic signal in the form of a superposition        of frequency components generated by the acoustic transmitters,        respectively, and allowing transmission of said generated        multi-frequency acoustic signal to another communication system;        and    -   (ii) upon receiving a multi-frequency acoustic signal,        processing the signal in accordance with data indicative of a        predetermined sequence of frequencies to thereby reconstruct a        data stream encoded within the received acoustic signal.

The acoustic signals can be transferred between the communicationsystems via a network formed by a plurality of acoustic transducerarrangements connectable to the network and configured for communicatingwith each other via the network. In this case, the digital data streamis also indicative of the network address of the respective acoustictransducer arrangement.

According to yet another aspect of the invention, there is provided amethod for using in data communication between remote communicationsystems, the method comprising generating an acoustic signalrepresentative of a modulated data stream, wherein said acoustic signalis a superposition of different frequency components in accordance witha predetermined sequence of frequencies.

According to yet another aspect of the invention, there is provided amethod for use in data exchange between communication systems, themethod comprising utilizing an acoustic transducer arrangementconfigured to carrying out the following:

receiving an electrical, RF or IR signal encoded with data coming from afirst communication system and addressed to a second communicationsystem; converting the received signal into a corresponding digital datastream; processing said digital data stream to translate it into apredetermined sequence of frequencies; concurrently operating an arrayof acoustic transmitters of the acoustic transducer arrangement togenerate a multi-frequency acoustic signal in the form of asuperposition of frequency components generated by the acoustictransmitters; and transmitting the generated multi-frequency acousticsignal to a second acoustic transducer arrangement associated with thesecond communication system;

receiving an external multi-frequency acoustic signal encoded withcertain data addressed to the first communication signal; and processingthe received acoustic signal in accordance with data indicative of apredetermined sequence of frequencies to thereby decode the data.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, a preferred embodiment will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIGS. 1A to 1C schematically illustrate several examples of acommunication technique according to the present invention;

FIG. 2 schematically illustrates an acoustic transducer arrangementaccording to one embodiment of the invention;

FIG. 3 illustrates flow diagrams of the main operational steps of thegeneration of a modulated acoustic wave indicative of a data sample, andthe demodulation of a received multi-frequency acoustic wave;

FIG. 4 illustrates the acoustic transducer arrangement according toanother embodiment of the invention; and

FIG. 5 exemplifies how the present invention can be used to providecommunication between medical devices and physician's personal portableunits within a hospital.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1A, there is schematically illustrated an acousticcommunication system 10A utilizing an acoustic transducer arrangementaccording to the invention. The system 10A is composed of first andsecond communication systems 12 and 14 (such as computer-, phone-,PDA-based systems) each associated with its own acoustic transducerarrangement, namely, is either connectable to the remote acoustictransducer arrangement via signal transmission or includes the acousticarrangement as its constructional part. In the present example of FIG.1A, the first and second systems 12 and 14 are equipped with theacoustic transducer arrangements 16A and 16B, respectively. The acoustictransducer arrangement 16A (or 16B) is configured as a chip with anembedded application preprogrammed for carrying out at least one of thefollowing: transmission of encoded acoustic data signals; and receivingand decoding acoustic data signals.

When operating in the transmission mode, the acoustic transducerarrangement operates to receive an input electrical, IR, RF or acousticdata stream carrying a signal produced by the respective communicationdevice, and to process the received data stream to generate an outputencoded data carrying acoustic signal. When operating in the receivingmode, the acoustic transducer arrangement is capable of receiving anencoded acoustic data carrying signal and processing it to generate adecoded electrical, IR, RF or acoustic data signal to be used for thedevice operation. The construction and operation of the acoustictransducer arrangement will be described further below with reference toFIGS. 2-4.

FIG. 1B more specifically illustrates a communication system 10B formedby two computer systems 12 and 14 configured for communication betweenthem via acoustic signal transmission. The system 12 includes a computerdevice 12A and an acoustic transducer 16A, which is connected to thecomputer device 12A via a processor unit 12B configured for carrying outdigital signal processing (DSP) and digital-to-analog (D/A) andanalog-to-digital (A/D) signal conversion. Similarly, the system 14includes a computer device 14A and an acoustic transducer 16B, which isconnected to the computer device 14A via a processor unit 14B configuredfor DSP, D/A and A/D functions.

Each of the transducers 16A and 16B is configured for both the datatransmission and data receiving modes. Considering data transmissionfrom the computer device 12A to computer device 14A, the system 10Boperates in the following manner:

The computer device 12A generates a digital data stream indicative ofspecific information addressed to computer 14A. To this end, thecomputer device utilizes an appropriate computer program and encodingutility typically provided in a computer device. This digital datastream is processed in the computer system 12 (in the processor unit12B) to be converted into an analog electronic signal, which operatesthe acoustic transducer 16A. The latter processes the receivedelectronic signal to convert it into an acoustic signal indicative ofthe encoded information, and outputs the signal to be transmitted to thecomputer system 14.

At the system 14, the acoustic signal is received and processed by theacoustic transducer 16B to be converted into an electronic signal, whichis then processed by the A/D and DSP of the processor unit 14B. Then,the so-processed digital signal is decoded and appropriately used by thecomputer device 14A (e.g., for operating a certain computer programand/or to be displayed on the computer monitor).

Referring to FIG. 1C, there is exemplified an acoustic communicationsystem 10C utilizing an acoustic network formed by the acoustictransducer arrangements according to the invention. The system 10C isthus formed by various communication stations 112, 114, 118, 120 and 122connectable to each other via a communication network formed by an arrayof acoustic transducer arrangements, generally at 16.

Generally, each of the communication stations 112-122 can be configuredas a server system capable of producing various data streams andappropriately distributing (routing) them in between the other stations,and being responsive to data signals coming from the other stations vianetwork. In the present example of FIG. 1C, the station 112 isconfigured as a server system, and the stations 114-122 are configuredas client stations.

It should be understood that the terms “server” and “client” used hereinsolely refer to the existence and absence, respectively, of a routerutility in the station. It should also be understood that each of thecommunication stations may comprise its associated acoustic transducerarrangement as a constructional part, or be connectable to a stand-alone(e.g., remote) acoustic transducer arrangement.

The communication station 112 (server) is a computer system equippedwith a data generating and processing utility (not shown) and a routerutility 112A, which is in turn equipped with or connected to theacoustic transducer arrangement 16A. The communication stations 114-122are constituted by, respectively, a medical measuring device (e.g.,ECG), PDA device, mobile phone device, and a PC device. These devices114-122 may and may not be equipped with the acoustic transducerarrangements. In the present example, the PC 122 is equipped with theacoustic transducer arrangement 16D, and the other devices 114-120 haveno integral acoustic transducers and receive electrical, RF or IRsignals (as the case may be) presenting a conversion of the acousticdata signal from the associated remote acoustic transducer arrangement16, which comprises an output utility configured for outputtingelectric, RF, IR and/or acoustic signal representative of the receiveddata, as will be described more specifically further below.

The system 10C operates in the following manner. The computer system 112(its data generator/processor) produces a digital data stream to betransmitted to a specific communication device, e.g., the ECG station114, via the communication network. The router utility 112A performsappropriate formatting of this data stream to be addressed to thespecific communication device via corresponding one or more nodes of thenetwork The acoustic transducer arrangement 16A, which is a node of theacoustic network, receives the formatted data stream, converts it intoan encoded acoustic signal and allows the transmission of this signalvia the network.

It should be understood that the router is preprogrammed to utilize anappropriate hash table representative of network addresses of thetransducer arrangements forming the network along with their associatednames, and preferably also utilizes a segmentation map representative ofa list of this IDs and names attached with the last known segment ID.The segmentation process thus consists of the following: the router thathas previously transmitted a message to a specific segment ID, waits fora notification from the transmitting element indicative of that thespecific network address along with the associated name corresponds tothat segment, and if not, the router retransmits the message to all thesegments. In the example of FIG. 1C, where the acoustic network isutilized, each acoustic transducer arrangement is assigned with itsunique identification code (network address) and these IDs are used forrouting the data streams in between the communication stations. In thisspecific example, each of the acoustic transducer arrangements ispreferably preprogrammed to identify the incoming signal to eitherprocess it as described above or just allowing the signal to beappropriately distributed to another acoustic transducer arrangement orthe communication station.

Reference is now made to FIG. 2 exemplifying the construction of theacoustic transducer arrangement 16 according to the invention. Thetransducer arrangement 16 is designed like an electronic card (chip withembedded application) and comprises an acoustic transmitter assembly 20,an acoustic receiver assembly 22, a control unit 24 that is connectableto the transmitter and receiver assemblies and to a network interfaceunit 26. The network interface unit 26 includes one or more signalinput/output ports—three such ports P₁-P₃ being shown in the presentexample configured for inputting/outputting RF, IR, and electricalsignals, respectively.

The transmitter assembly 20 is composed of an array of acoustictransmitters (e.g., piezoelectric crystal elements)—four suchtransmitters 20A-20D being shown in the present example, operable by thecontrol unit 24 via an oscillation generator and voltage supply assembly21. According to the technique of the present invention, the operationalfrequencies of the acoustic arrangement are of the ultrasound range,higher than 20 kHz.

The receiver assembly 22 comprises one or more acoustic receivers (e.g.,piezoelectric crystals)—two such receivers 22A and 22B being shown inthe present example. The received acoustic data is transmitted to thecontrol unit 24 via a frequency filter arrangement 23, which includes a“static” filter 23A that blocks frequencies below the selectedultrasound range, and, in the case of more than one receiver, includesalso a frequency sub-divider unit 23B.

The known piezoelectric phenomenon consists of converting a mechanicaldeformation into a voltage, and the counter piezoelectric phenomenonconsists of converting a voltage into a mechanical deformation. Thepiezoelectric element is typically formed by a substrate of apiezoelectric material (quartz resonator) that is preferably very thin(of about several micrometers) to enable the generation of highfrequency acoustic waves; and includes electrodes on opposite faces ofthe substrate. The electrodes are connected to a high-frequency voltagesource, which operates through the electrodes to cause the lengthwisevibration in the piezoelectric substrate.

The present invention provides for combining several piezoelectriccrystal elements 20A-20D together to concurrently produce a wide-rangemulti-frequency acoustic signal, and to enable modulation of thesefrequencies (i.e., perform a signal encoding) in accordance with a datastream to be transmitted. This enables simultaneous transmission ofmultiple frequency components indicative of a multi-bit data streamsample (formed by one or more “words”), rather than bit-by-bittransmitting a data sample using a single transmitter element. Since inorder to generate an acoustic wave of a specific frequency by apiezoelectric crystal, the voltage supply is to satisfy the resonancecondition of the crystal, the higher the number of crystals in thetransmitting array, the more frequencies can be concurrently generated.

As for the receiver assembly 22, generally, the provision of onereceiver would be sufficient for the purposes of the present invention,but preferably at least two such receivers (i.e., receiver array) areused thereby allowing detection of a wide range of acoustic wavefrequencies and concurrent decoding of the entire received sample. Itshould, however, be understood that since the acoustic signal detectionis not limited by the resonance condition of the crystal, the receiverarray may include a smaller number of crystal elements than thetransmitter array.

The control unit 24 includes a memory (RAM) 24A, a microprocessor 24Bthat is connected to the oscillation generator 21 and to the filterarrangement 23 via a logic utility 24C and a clock utility 24D. Itshould be noted, although not specifically shown, that also provided inthe transducer arrangement 16 are such functional utilities as anD/A-A/D converter, and amplifiers for amplifying the input signal to beconverted into an encoded acoustic signal and amplifying the electricalsignal representative of the received acoustic signal.

The operational steps of the acoustic transducer arrangement 16 will nowbe described with reference to FIG. 3. In the data transmission mode,the acoustic transducer arrangement 16 operates as follows:

-   -   The control unit 24 receives a digital data stream from one of        the input utilities (or from the router, or directly from the        data generation of a computer device, medical device or any        other kind of data generator as the case may be), and stores the        received digital data stream in an appropriate format.    -   The control unit 24 processes the received digital data stream        by slicing it into samples that are of a predefined fixed length        (e.g., 4 or 8 bits in a sample). For example, 106 Hexadecimal        values can be used, each Hexadecimal value being representative        of 4 bits, thus having 53 samples. The control unit 24 (the        clock and logics thereof) then operates to generate a        corresponding sequence of voltages in accordance with the        predefined order of the transmitters' frequencies in the array.    -   The so-produced sequence of voltage it used to operate the        oscillation generator 21 to provide the respective        voltage-sample. The oscillation generator 21 thus operates the        transmitters 20A-20D via their electrode assemblies to        simultaneously produce acoustic signal components representative        of the data sample. To this end, each of the transmitters is        responsible for generating an acoustic wave of a predefined        frequency (corresponding to its resonance condition), and        preferably also predetermined amplitude, as will be described        further below.

The multiple-transmitter assembly 20 (crystal elements 20A-20D) is thusoperable to concurrently produce a multi-frequency acoustic waveindicative of a data sample to be transmitted. As will be describedfurther below with reference to FIG. 4, a two-frequency acoustic wavecan be achieved with a single crystal.

In the receiving mode, the transducer arrangement 16 operates asfollows:

-   -   Each of the acoustic receiving elements 22A and 22B always        “listens” for incoming signals, i.e., is continuously responsive        to incoming acoustic signals to cause the generation of        respective voltage outputs. As the incoming signals generated by        the acoustic transducer arrangement of the present invention are        in a specific, very high range of acoustic frequencies, a simple        high pass band filtering can be used. Thus, the voltage output        of the receivers undergoes high-pass frequency filtering, namely        voltages corresponding to frequencies outside the predetermined        range (e.g., lower than the predetermined range, i.e., lower        than 20 kHz) are prevented from being detected; and undergoes        the sub division in accordance with the frequency ranges of the        receivers.    -   The filtered signal (after being sampled from the piezoelectric        crystals) is stored in a Pulse Code Modulation (PCM) wave        format, which is practically the voltage representation of the        sampled crystals, and the data sample can therefore be stored in        a RAM unit. The logic utility thus identifies the timing of the        incoming frequencies, and operates together with the        microprocessor to store the voltage values in the RAM.    -   Then, the microprocessor operates to apply the Fast Fourier        Transform (FFT) to the stored voltage series. The result of the        FFT is the frequency map indicative of which frequency        represents digital “0” and “1” values.    -   The microprocessor analyzes the frequency map and performs an        error correction to restore (decode) the received signals.    -   Having decoded the received signal, the control unit 24        identifies the ID of an electronic device to which this specific        data stream is addressed, and actuates the selective port to        transmit the signal to the respective communication device in        the form of RF, IR or electrical signal. The case may be such        that while decoding the first received signal, the        microprocessor identifies that the signal is addressed to        another acoustic arrangement of the network (i.e., identifies        the network address of the specific acoustic arrangement        appearing in the first received sample). In this case, the        control unit will operate the transmitter assembly 20        accordingly to retransmit the received signal in the acoustic        form via the network.

The use of multi-frequency acoustic waves based communication(multi-frequency transmission at a given time) enables frequencymodulation or frequency and amplitude modulation of the acoustic signalto be indicative of the entire data sample. This features of theacoustic transducer arrangement of the present invention allows for itsadvantageous use in device-to-device communication, as compared to theproposed prior art technique (utilizing a single pair of acoustictransmitter and receiver) and to the conventionally used electromagneticwaves based communication where only one frequency can be received (andtherefore broadcasted) at a given time (limited by a tuning problem).Another advantageous feature of the technique of the present inventionis the operation with high-frequency acoustic waves and specific signalmodulation (as exemplified above and as will be exemplified furtherbelow), which requires much less sophisticated noise-filteringtechniques, as compared to the known communication techniques.

Thus, in the transmission operational mode, the control unit operates toapply a frequency coding to the acoustic signal, such that the generatedacoustic signal is a superposition of sinusoidal signals of multiplefrequency components indicative of a multi-bit data stream sample. Inthe receiving operation mode of the transducer arrangement, the controlunit processes the electrical outputs of the receiver(s) (22A and 22B inFIG. 2) to concurrently decode the received multi-frequency codedmulti-bit data sample by applying a time-to-frequency domaintransformation (Fourier transform) thereto, thereby obtaining amulti-bit spread spectrum. This spectrum is analyzed, preferably usingan error correction, to identify the predetermined frequencies withinthe received sample and to translate the sample into a digital datastream.

The encoding of the multi-frequency acoustic wave indicative of a datasample may consist of the following. The first transmitter in the array(transmitter 20A) is operable to generate the so-called “basicfrequency”, e.g., f₁=50 kHz, and all the other transmitters 20B-20Dgenerate frequencies spaced from the basic frequency a predefinedspacing, such that f₂=51 kHz, f₃=52 kHz, f₄=53 kHz, respectively. Theexistence or absence of the specific frequency in the transmittedfrequency-sample is indicative of respectively logic “1” or “0”. Itshould be understood that this is a specific example of the number oftransmitters in the array and the frequency values and spacings betweenthem. Using a higher number of transmitters enables concurrentlytransmitting a larger data sample. Thus, a wave-form signal is createdby concurrently transmitting all the four frequencies during apredefined fixed time length (for example 200 milliseconds).

For example, the 4-bit word “1001” (data sample) can be transmitted byconcurrently generating frequencies f₁-f₄ at amplitudes A₁=90, A₂=0,A₃=0, A₄=90. The data sample may also be amplitude modulated. Thismodulation may be based on a predefined range for each of the amplitudesA₁-A₄, and/or a specific key, e.g., the sum of amplitudes of 1^(st) and3^(rd) bits and 2^(nd) and 4^(th) bits in the sample, or an amplitudedifference between the adjacent frequencies in the received frequencystream. In other words, the amplitudes of the existing frequencies canbe varied in a certain predefined order, known to the receiver. Forexample, the amplitude difference being higher than a certain predefinedthreshold is considered as corresponding to “1”, and the amplitudedifference being lower than the threshold is considered as correspondingto “0”.

While decoding (demodulating) the received signal, the appropriate errorcorrection is carried out. Considering the simple amplitude modulationof the acoustic signal, the error correction can be based on checkingfor the amplitudes order in the received signal, or a certain thresholdfor an amplitude difference between the adjacent frequencies in thereceived frequency stream.

The following is a specific, non-limiting example, of encoding theacoustic signal to concurrently transmit a data sample in the form oftwo 4-bit words, and an error correction performed while decoding thereceived signals. In this specific example, four-element transmitterassembly is considered, and the operational (resonance) frequencies offour crystal resonators are f₁=50 kHz, f₂=51 kHz, f₃=52 kHz, and f₄=53kHz, respectively. Thus, the signal encoding utilizes the specific orderof frequencies f₁, f₂, f₃, f₄ in the four-frequency acoustic signal.Additionally, in order to enable concurrent transmission of the entiredata sample formed by two 4-bit words, the acoustic signal is amplitudemodulated. The amplitudes used for transmitting the frequencies f₁-f₄are for example as follows: 0<A₁<30; 30<A₂<60; 60<A₃<90; 90<A₄<127. Inorder to enable error correction at the receiving side, a certain key isused, for example “0101010 . . . ”.

Let us consider the transmission of 4-bit words W₁=1000, W₂=1010,W₃=1001, W₄=0001, W₅=0010 and W₆=1001, wherein two 4-bit words W₁ and W₂present the first data sample to be concurrently transmitted by fourcrystal resonators, two 4-bit words W₃ and W₄ present the second datasample, and two 4-bit words W₅ and W₆ present the third data sample.When transmitting the first data sample, four crystal resonatorsgenerate acoustic signals representative of symbols “11”, “00”, “01” and“00”, respectively. The position of each symbol in the sample isrepresented by the respective frequency in accordance to the predefinedorder of frequencies. According to the selected key, symbol “11” whenappearing for the first time or for the first time after transmission ofsymbol “00” is represented by the maximal value of amplitude A₄, i.e.,127, and a further appearing of this symbol prior to “00” is representedby any other value of A₄ range, preferably the center point of therange. Consequently, symbol “00” is represented either by the minimalvalue of amplitude A₁, i.e., zero (when appearing for the first timeafter symbol “11”), or by any other value of A₁ range (preferably, thecenter point of this range). Symbols “01” and “10” are represented byamplitudes A₂ and A₃, respectively, preferably at the center values ofthe selected ranges. Thus, in this specific example, the multi-frequencyacoustic signal representative of six 4-bit words contains threesequentially generated data samples, wherein each sample is concurrentlygenerated as a four-frequency acoustic signal: (f₁=127, f₂=0, f₃=45,f₄=15), (f₁=65, f₂=15, f₃=15, f₄₌₁₂₇), (f₁=45, f₂=0, f₃=75, f=45). Atthe receiver side, this acoustic signal is translated using the abovekey, and upon detecting an error (no correspondence with the key), therespective sample is identified and transmitted back with a request forretransmitting the sample again.

Another possible example of signal encoding/decoding consists of usingsecond harmonics of each frequency in the sequence. In this case, theresonance frequency of each transmitter (crystal resonator) is selectedto be other than the second harmonic of another resonator frequency.Thus, alternatively to the above-described amplitude modulation or inaddition thereto, the second harmonic of each resonant frequency may beused as a key for encoding the signal and carrying out the errorcorrection.

As indicated above, a transmitter in the multi-transmitter assembly cangenerate a two-frequency acoustic wave while utilizing a single crystalresonator. This is schematically illustrated in FIG. 4. To facilitateunderstanding, the same reference numbers are used to identify thosecomponents that are common in the examples of FIGS. 2 and 4. An acoustictransducer arrangement 216 of FIG. 4 has a transmitter assembly 220equipped with at least one electrically conductive membrane M (thinelectrode) associated with one or more crystal elements in the array. Inthe present example, the membrane (or four separate membrane segments)is provided at the output of all the crystal resonators. If the membraneis in its inoperative position (no voltage is applied to the membrane),a single-frequency acoustic wave generated by the respective crystalresonator propagates through the membrane while being unaffected by themembrane.

If the membrane is shifted to its operative position by applying acertain voltage thereto, this results in a membrane vibration with acertain frequency (typically slightly different from the resonancefrequency of the respective crystal element). Considering the acoustictransmitter element 20A: in the inoperative position of the membrane, asignal component produced by this acoustic channel has a frequency f₁corresponding to the resonance frequency of said membrane segment; andin the operative position of the membrane oscillating with a frequencyf₅, the signal component of this acoustic channel has a frequency of(f₁+f₅). The other acoustic channels operate in a similar manner, asshown in the figure in a self explanatory manner.

Hence, the passage of a single-frequency acoustic wave generated by aspecific crystal element through the operative membrane will result in atwo-frequency acoustic wave. Thus, eight-frequency acoustic wave (8-bitdata sample) can be produced by four-crystal array with membranes. Ifappropriate amplitude modulation is used, for example that describedabove, 16-bit data sample can be generated by the four-transmitterassembly with membranes.

Reference is now made to FIG. 5 showing a specific non-limiting exampleof how the present invention can be used to provide communicationbetween medical devices (and/or any other devices) located in ahospital, wherein such devices may include an Intensive Care Unit orIntermediate Care Unit associated with a patient being monitored andportable units (PDAs) carried by the medical staff. A system, generallyat 300 is configured as an Acoustic Medical Intelligent Alert System(AMIAS). The system is formed by multiple communication devices, eachassociated with a respective station in the hospital, and connected toan acoustic network formed by acoustic transducer arrangement of thepresent invention. In the present example, each portable unit (PDA)carried by doctors is associated (equipped) with its own acoustictransmitter/receiver ATR constructed as described above with referenceto FIG. 2 or 4, and the acoustic network is formed by the so-called“Acoustic Gateways” or (AGW) that are actually acoustictransmitter/receivers of the present invention but are functionallydistinguished from ATRs in that AGW is a stationary mounted unit coupledto the LAN while ATR is a mobile unit that can be attached to the PDA(or another portable computer or monitoring device) or integrated withthe PDA as a chip with embedded application.

The AMIAS 300 utilizes Acoustic Wireless Local Area Network (AWLAN)communication and is targeted to serve places in which there is a needfor alert messages to be transferred immediately from the generatingdevice to various destinations where high frequency transmission isforbidden for use. This is achieved by using a high frequency acoustictransmission technique (ultrasound) of the present invention enablingfor providing either a complementary service to organizations that arealready using RF based WLAN systems or a complete solution toorganizations which do not have any type of WLAN support. The AMIAS 300solves a major obstacle which prevents any traditional WLAN, based onradio frequency transmission, from being used in places where missioncritical sensitive medical equipment is located and operated and issubject to malfunction due to RFI caused by the RF WLAN system.

The system 300 is thus formed by a central station 302 (AMIAS server);the acoustic network represented by a plurality of AGWs, generally at304; and a plurality of ATRs 316 each associated with a respectiveportable unit (PDA) of the medical stuff. The AMIAS server 302 isconnected to a Hospital Server (via wires or wireless), and is connectedvia a local area network (LAN) of the hospital to the acoustic networkto a Nurse/Doctor Station and a plurality of medical device associatedwith patients.

The AMIAS is configured and operated to transfer emergency alertsgenerated by the medical devices to their destinations. The medicaldevices thus serve as the input sources to the system.

To enable a medical device to communicate with the AMIAS server, themedical device has an output interface to which all alerts and relatedinformation are transferred, and an output interface for transmittingall relevant information in digital format to the AMIAS server 302. Themain functions of the medical device include: analysis of signalsreceived from a respective monitoring system associated with a patient,generation of emergency alert and data related to the alert situation,and transmission of the alert and related data to the output interfaceof the device.

It should be noted that the medical devices can be hooked directly tothe AMIAS server or via their dedicated ATRs. Direct connection isimplemented using such communication methods as wired LAN or Phonesystem (using the hospital's infrastructure).

As shown in the figure, the medical devices are connected to the LAN viaa COM unit, which is an electronic unit configured to operate like aswitch or hub that distributes information coming to/from the server 302to the AGWs and computers or other devices. COM unit thus provides aninterface between various types of medical devices to the AMIAS server(via LAN).

The ATR 316 is a two way acoustic transducer configured as describedabove with reference to FIG. 2 or FIG. 4. The ATR receives digitalelectronic data from the respective PDA and converts it into an acousticsignal that is being transmitted to other components of the system, andreceives acoustic signal coming from the network (AGW) and converts itinto a digital format to be presented at the PDA. ATR can be hooked toseveral types of medical devices, portable units and interfaces betweeneach of them and the nearest AGW 304. The main functions of the ATR 316include: provision of interface software between the AGW 304 and themedical devices; interface software between the AGW and the AMIAS server302; and interface between the AGW 304 and a Portable Unit.

The AGW 304 is a two way acoustic transducer configured similar to ATR316, for maintaining the acoustic network. AGW is a gateway thatcommunicates with all acoustic ATRs and with the AMIAS server. AGW canreceive digital electronic data or RF data, convert it into acousticsignal and transmit the signal to the addressed utility of the system,as well as receive acoustic signals, convert them to digital electronicor RF data and transmit it through wire or RF communication. The AGW isthus configured to provide an interface between the AMIAS server and theATRs connected to the medical devices; and an interface between theAMIAS server and the ATRs connected to portable units.

The portable PDAs serve as remote monitors to which all alertinformation is addressed. They are carried by authorized personnelallowing them to receive all emergency information as it is transmitted,regardless of their location. The portable PDA is configured forcommunicating with the acoustic network through ATR, upon receiving analert generating an alarm signal (buzzer or vibration) and displayinginformation on a local screen, thus allowing users to generate aresponse to the alarm generator either by keyboard, keypad, touch screenor any kind of interface.

The AMIAS server 302 is a computer server including all the informationrequired to control the system operation. It serves as a central pointof the system and is configured for carrying out the following:receiving all the alerts and related data coming from the medicaldevices (through ATRs or LAN), processing the received alerts andrelated data and adding required information retrieved from the centraldatabase, addressing the alert and related data to the appropriateportable unit(s), receiving responses from the portable units andaddressing the responses to appropriate destinations and to theNurse/Doctor station, communicating with the Nurse/Doctor station, andcommunicating with the main hospital server. The AMIAS server maintainsthe database (or is connected to the database at the hospital server) ofall data necessary to manage day to day operation of the alert system aswell as its history. The AMIAS server allows several levels ofauthorization for conducting different operations.

Nurse/Doctor station is a PC based station appropriately located in thedepartment. More than one station can be used within the samedepartment. This station is used by “on duty” doctor and/or nurse tomonitor all the activities of the system 300 (over the network). Thisstation displays medical status of all activity to the “on duty”nurse/doctor, allows this nurse/doctor for generating alarm to each oneof the portable devices, and for generating a response to any givenalarm.

The hospital server contains medical information as well asadministrative information regarding all the patients in the hospital.The hospital server actually serves as input/output channel for theAMIAS server. With regard to the AMIAS server, the hospital servercarries out the following: provides necessary administrative informationto the AMIAS server while setting up the AMIAS server, provides medicalinformation to the AMIAS server upon request from one or more portableunits, and collects the AMIAS activity information from time to time andupdates it in the database.

Thus, the system 300 operates as follows: The medical device, whilemonitoring certain condition(s) of a specific patient, identifies analert condition, generates digital data indicative thereof (containingall critical situation related information), and transmits this dataeither directly to the AMIAS server (through the respective COM) or tothe local ATR connected to the medical device. The data sent through theATR will be converted by this ATR to acoustic signal and transmitted tothe nearest AGW. The acoustic signal received by the nearest AGW, willbe converted to digital data and transferred to the AMIAS server(alternatively, the data is directly received by the AMIAS server viathe COM unit).

The AMIAS server processes the received digital data, retrievesnecessary information from the database, adds this information to thereceived data, identifies the destination and sends modified message(after deleting irrelevant information and adding complementaryinformation as retrieved from the AMIAS server) to the AGWs and also toNurse station via the LAN.

At the AGW, the received data is converted into acoustic signal andtransmitted through the acoustic network. The portable device carried byauthorized personal (doctor, nurse or any other authorized medical teammember) receives the acoustic signal via its local/attached ATR. Thelatter converts the acoustic signal into digital data and transfer it tothe PDA, which in turn generates alarm sounds and/or vibrations anddisplays data on its local screen to be read by the person carrying theportable unit. The authorized person (doctor) operates his portable unitto respond to the message. This response is transmitted in digital formto the local ATR of the portable unit. The ATR converts this digitaldata into acoustic signal and transmits it to the nearest AGW. Thisacoustic signal is received by the nearest AGW, converted to digitaldata and transferred by to the AMIAS server via the LAN. At the AMIASserver, the response is processed and transmitted to the Nurse/Doctorsstations via the LAN.

The system 300 can operate in two modes: complementary mode or fullservice mode. The complementary mode supports cases in which thehospital is already using existing WLAN environment except for areasthat are specifically sensitive to RFI segments and that could andshould be covered by AMIAS. In this mode, there is no need to supportthe full system functionality and it can take advantage of the existingenvironment such as database and other software features. The fullservice mode supports cases in which the hospital has no WLAN solution,and therefore the system provides complete and enhanced controlfunctionality. Thus, the technique of the present invention provides forusing acoustic-only data communication network or a combination of theacoustic network with the conventional LAN or RF network. The presentinvention thus provides a complete solution for fast and safecommunication between various devices, and especially provides benefitfor communication within a hospital.

Those skilled in the art will readily appreciate that variousmodifications and changes can be applied to the embodiments of theinvention as herein before exemplified as defined in and by the appendedclaims.

1. An acoustic transducer arrangement comprising: an acoustictransmitter assembly including an array of transmitter elementsconfigured to generate together a multi-frequency acoustic signal, theacoustic transmitter assembly comprising at least one electricallyconductive membrane accommodated in a path of an acoustic wave componentgenerated by one or more of the transmitter elements and operating tooscillate with a frequency different from that of said acoustic wavecomponent, a number of the multiple different frequency componentsforming the acoustic signal being thereby higher than the number of thetransmitter elements in the array; and a control unit preprogrammed tooperate the acoustic transmitter assembly in accordance with a digitaldata stream indicative of a received signal to generate themulti-frequency acoustic signal indicative of the received data stream.2. The acoustic transducer arrangement of claim 1, comprising anacoustic receiver assembly configured to receive a multi-frequencyacoustic signal, the control unit being preprogrammed to process datarepresentative of the received acoustic signal to demodulate it into anoutput data stream and for operating an output utility to output thedemodulated data, representative of the received multi-frequencyacoustic signal, in a predetermined format.
 3. The acoustic transducerarrangement of claim 2, wherein the acoustic receiver assembly comprisesat least two acoustic receivers.
 4. The acoustic transducer arrangementof claim 2, wherein the demodulation of the received acoustic signalincludes an error correction.
 5. The acoustic transducer arrangement ofclaim 4, wherein the error correction utilizes a certain key in the formof a predetermined digital stream periodicity in the received acousticsignal.
 6. The acoustic transducer arrangement of claim 2, wherein thecontrol unit is configured to apply an amplitude modulation to thefrequency components, the demodulation of the received acoustic signalincluding an error correction, the error correction being based on oneof the following: checking for the amplitudes order in the receivedacoustic signal; and checking for a certain threshold for an amplitudedifference between the adjacent frequencies in the received frequencystream.
 7. The acoustic transducer arrangement of claim 1, comprising atleast one input and output port for inputting and outputting a datastream in the form of at least one of the following signal formats:radio-frequency signal, infra-red signal, and electrical signal, thecontrol unit being connected to the input and output port for receivingthe data stream that is to be transmitted through the transmitterassembly as an acoustic signal.
 8. The acoustic transducer arrangementof claim 1, wherein each of the transmitter elements of the transmitterassembly has a resonance frequency different from that of the otherelements and is independently operated by the control unit to generatean acoustic wave component, the generated multi-frequency acousticsignal being a superposition of sinusoidal signals of the multipledifferent frequency components.
 9. The acoustic transducer arrangementof claim 8, wherein the resonance frequency of the transmitter elementis higher than 20 kHz.
 10. The acoustic transducer arrangement of claim1, wherein each of the transmitter elements is formed by an oscillatingelement characterized by a specific resonance frequency, a number of themultiple different frequency components being equal to the number of thetransmitter elements in the array.
 11. The acoustic transducerarrangement of claim 1, wherein said at least one electricallyconductive membrane is accommodated in the paths of all the acousticwave components generated by the transmitter elements.
 12. The acoustictransducer arrangement of claim 1, wherein the control unit isconfigured to modulate the output data stream to be indicative of anetwork address of an associated communication station connectable to acommunication network.
 13. The acoustic transducer arrangement of claim1, wherein the control unit is configured to frequency modulate theoutput acoustic signal in accordance with a predetermined sequence offrequencies.
 14. The acoustic transducer arrangement of claim 13,wherein the frequency components generated by the transmitter elementsare spaced from each other by a predetermined value.
 15. The acoustictransducer arrangement of claim 14, wherein said frequency modulation issuch that a presence in the multi-frequency acoustic signal of aspecific one of frequency components of said predetermined sequence offrequencies is indicative of binary “1” and absence of a specificfrequency component is indicative of binary “0”.
 16. The acoustictransducer arrangement of claim 1, wherein the control unit isconfigured to apply an amplitude modulation to the frequency components.17. The acoustic transducer arrangement of claim 16, wherein theamplitude modulation utilizes at least one of the following: is based onthat the amplitudes of the frequency components in the multi-frequencystream vary in a certain predefined order; is based on that each of theamplitudes of the frequency components generated by the transmitterelements is within a predefined range; is based on a specific keydefining a certain sum of the amplitudes of specific bits in the datasample; and is based on a specific key defining a certain differencebetween the amplitudes of the adjacent frequency components in themulti-frequency stream.
 18. A communication device connectable to acommunication network, the device comprising an acoustic transducerarrangement comprising: an acoustic transmitter assembly including anarray of transmitter elements operable to generate together amulti-frequency acoustic signal, the acoustic transmitter assemblycomprising at least one electrically conductive membrane accommodated ina path of an acoustic wave component generated by one or more of thetransmitter elements and operating to oscillate with a frequencydifferent from that of said acoustic wave component, a number of themultiple different frequency components forming the acoustic signalbeing thereby higher than the number of the transmitter elements in thearray; and a control unit preprogrammed to operate the acoustictransmitter assembly in accordance with a digital data stream indicativeof a received signal to generate the multi-frequency acoustic signalindicative of the received data stream.
 19. A communication systemcomprising at least two communication devices connectable to each otherthrough at least one acoustic transducer arrangement comprising: anacoustic transmitter assembly including an array of transmitter elementsoperable to generate together a multi-frequency acoustic signal, theacoustic transmitter assembly comprising at least one electricallyconductive membrane accommodated in a path of an acoustic wave componentgenerated by one or more of the transmitter elements and operating tooscillate with a frequency different from that of said acoustic wavecomponent, a number of the multiple different frequency componentsforming the acoustic signal being thereby higher than the number of thetransmitter elements in the array; and a control unit preprogrammed tooperate the acoustic transmitter assembly in accordance with a digitaldata stream indicative of a received signal to generate themulti-frequency acoustic signal indicative of the received data stream.20. A method for use in data exchange between communication systems, themethod comprising utilizing an acoustic transducer arrangementconfigured to carrying out the following: receiving an electrical, RF orIR signal encoded with data coming from a first communication system andaddressed to a second communication system; converting the receivedsignal into a corresponding digital data stream; processing said digitaldata stream to translate said digital data stream into a predeterminedsequence of frequencies, said processing comprising slicing said digitaldata stream into samples that are of a predefined fixed length andgenerating a corresponding sequence of voltages in accordance with thepredefined order of frequencies of the transmitters in the array, saidsequence of voltage being used for the operation of said array of theacoustic transmitters; concurrently operating an array of acoustictransmitters to generate a multi-frequency acoustic signal in the formof a superposition of frequency components generated by the acoustictransmitters; and transmitting the generated multi-frequency acousticsignal to a second acoustic transducer arrangement associated with thesecond communication system.
 21. The method of claim 20, comprising:receiving an external multi-frequency acoustic signal encoded withcertain data addressed to the first communication system; and processingthe received acoustic signal in accordance with data indicative of apredetermined sequence of frequencies to thereby decode the data. 22.The method of claim 20, wherein the generated acoustic signal istransferred to the second communication system via a network formed by aplurality of the acoustic transducer arrangements communicatable witheach other.
 23. The method of claim 22, wherein the data is indicativeof the network address of the respective acoustic transducerarrangement.
 24. The method of claim 20, wherein each of saidfrequencies is higher than 20 kHz.
 25. The method of claim 20, whereinsaid processing of the digital data stream includes frequency modulationof the acoustic signal to be transmitted, in accordance with apredetermined sequence of frequencies.
 26. The method of claim 25,wherein the frequency components generated by the transmitter elementsare spaced from each other by a predetermined value.
 27. The method ofclaim 26, wherein said frequency modulation is such that a presence inthe multi-frequency acoustic signal of a specific one of frequencycomponents of said predetermined sequence of frequencies is indicativeof binary “1” and absence of a specific frequency component isindicative of binary “0”.
 28. The method of claim 20, wherein saidprocessing of the digital data stream comprises an amplitude modulationof the data stream.
 29. The method of claim 28, wherein said amplitudemodulation utilizes at least one of the following: comprises assigningto each of the frequencies a certain amplitude in accordance withpredefined amplitude ranges for said frequencies; is based on that theamplitudes of the frequency components in the multi-frequency streamvary in a certain predefined order; is based on that each of theamplitudes of the frequency components generated by the transmitterelements is within a predefined range; is based on a specific keydefining a certain sum of the amplitudes of specific bits in the datasample; and is based on a specific key defining a certain differencebetween the amplitudes of the adjacent frequency components in themulti-frequency stream.
 30. The method of claim 20, wherein the decodingof the received acoustic signal includes an error correction, the errorcorrection being based on one of the following: checking for theamplitudes order in the received acoustic signal; and checking for acertain threshold for an amplitude difference between the adjacentfrequencies in the received frequency stream.
 31. The method of claim28, wherein the decoding of the received acoustic signal includes anerror correction.
 32. The method of claim 30, wherein the errorcorrection utilizes a certain key in the form of a predetermined digitalstream periodicity in the received acoustic signal.